How to define terms according to the IBO


The following definitions are organized according to topic, with the SL and HL sections combined. If you are looking for the definition of a specific term, just use the search function in your internet browser (Ctrl + F). Add each definition in its new row. To add a new row, click in the row that you want to add your definition under, click on the small "tables" button that appears, go to "row", and choose "add row below". If you are having problems doing that, send me an email and I'll add the definition.

I went through the syllabus using the search function and found all the syllabus objectives that start with "define". We should know the definitions for these words as they are explicitly specified in the syllabus. I made a (very small) start with the easy ones. Feel free to add or make changes. (Aki)
Mechanics (Topic 2)
displacement
Distance traveled in a specified direction. The shortest (straight-line) distance between two points.
velocity
Rate of change of dispacement. Rate of distance traveled in a specified direction.
speed
Distance traveled per unit time.
acceleration
Rate of change of velocity.
momentum (linear)

impulse
Rate of change of momentum.
power
Average energy consumed per unit time.
efficiency
Ratio of useful energy output to the total energy input.


Thermal Physics and Thermodynamics (Topics 3 & 10)
mole

molar mass

Avogadro's Constant
There is 6.02 * 10^23 molecules/atoms in 1 mole of a substance.
specific heat capacity

thermal capacity

specific latent heat

pressure
The force per unit area exerted on a surface.
ideal gas
Definition depends on question: In general, an ideal gas obeys PV = nRT. There are no forces between molecules for all conditions of P, V and T. If definition asks in terms of kinetic molecular theory - no intermolecular forces, volume of gas molecules is negligible, collisions are perfectly elastic (do not state Ideal Gas Law in this case)


Waves (Topics 4 & 11)
displacement

amplitude
Maximum displacement from the equilibrium position (denoted x0).
frequency
The number of oscillations per second (denoted f).
period
The time taken for one entire oscillation (denoted T)
phase difference

simple harmonic motion

wavelength
The distance between successive, corresponding points in a wave.
wave speed

intensity



Electric Currents & Electromagnetic Induction (Topics 5 & 12)
electrical potential difference

electronvolt
The energy gained by an electron when it travels through a potential difference of 1 V (1 eV = 1.60 * 10^-19 J)
electric current

resistance

electromotive force



Lenz's Law
the induced emf is induced in such a direction so that the effect of the induction is to oppose the change that caused it.
magnetic flux

magnetic flux linkage



Motion in Fields (Topics 6 & 9)
electric field strength
the force per unit charge exerted on a small positive test charge in an electric field
gravitational field strength
the force per unit mass exerted on a point/small/test mass in a gravitational field
gravitational potential
energy per unit mass, i.e. the potential energy change (work done) per unit of mass, in moving the test mass from infinity (where potential = zero) to a point in the gravitational field. Gravitational potential is always negative value that approaches zero at infinity i.e. potential energy decreases when the point mass is moved from infinity toward the source of the field.
gravitational potential difference
energy change (work done) per unit mass to move between two points in the field. If potential difference is positive - the potential energy per unit mass is increasing and work is done against the field.


Atomic and Nuclear Physics & Quantum Physics (Topics 7 & 13)
nucleon number
The total number (protons + neutrons) in a nucleus. Aka the mass number.
proton number
The number of protons in a nucleus.
neutron number
The number of neutrons in a nucleus.
radioactive half-life
The amount of time it takes a naturally radioactive sample to decay to half of its original amount.
unified atomic mass unit

mass defect

binding energy

binding energy per nucleon



decay constant

Energy, Power, and Climate Change (Topic 8)
energy density

albedo

surface heat capacity

coefficient of volume expansion



Digital Technology (Topic 14)
capacitance
amount of charge that a capacitor can store for a given potential difference
least significant bit
the bit that represents the smallest decimal number
quantum efficiency
the ratio of the number of electrons emitted to the number of photons incident on the pixel
magnification
ratio of the length of the image on the CCD to the length of the object


Astrophysics (Option E) - adamblackburn adamblackburn
asteroid
small rocky body that drifts around the solar system
meteoroid
an asteroid on a collision course with a planet
meteorites
the parts of a meteoroid that arrive on a planet's surface
comets
mixtures of rock and ice in very elliptical orbits around the sun
constellations
patterns of stars that appear close to each other as observed from Earth
astronomical unit
distance from the Sun to the Earth (1.5*10^11m)
parsec
a unit of length; a line 1 AU subtends an angle of 1 arcsecond at one parsec (3.26 light years)
light year
distance light travels in one year (9.5*10^15m)
galaxy
a group of many (billions) stars that are physically close to each other
luminosity
the total power radiated by a star (w)
apparent brightness
the power received by an observer on Earth (w/m^2)
absolute magnitude
apparent magnitude that a star would have if it were observed from a distance of 10 parsecs
apparent magnitude
a logarithmic scale for measuring brightness where the lower the number, the brighter the star
red-shift
the color shift of a receding star
blue-shift
the color shift of an approaching star
spectral class
groups of stars based on their spectra of light; each group has a different surface temperature range
red giant
large, red stars that are relatively cool
red supergiant
large red giants
white dwarf
small, white stars that are relatively hot; a final stage for some stars in which fusion does not take place
cepheid variables
slightly unstable stars that have a regular variation in brightness thought to be an oscillation in the size of the star
binary stars
a system involving two stars
visual binary
a binary system that can be distinguished using a telescope
spectroscopic binary
a binary system that can be distinguished from the analysis of the spectrum of light coming from the system
eclipsing binary
a binary system that can be distinguished because of the periodic change in brightness
Hertzsprung-Russell diagram
a graph of luminosity (logarithmic) vs. decreasing temperature
main sequence
'normal', stable stars fusing hydrogen to helium whose only difference is mass
parallax
the apparent movement of the star when compared to very far objects
spectroscopic parallax
the procedure whereby the luminosity of a star is estimated from its spectrum
Olbers' paradox
an infinite, uniform, static universe will have a night sky that is bright
background microwave radiation
radiation at of a temperature of 3K produced that is the radiation of the Universe itself
open Universe
a Universe that continues to expand forever
closed Universe
a Universe that will eventually come to a stop and collapse back in on itself via the force of gravity
flat Universe
a Universe that is neither open or closed that will take an infinite amount of time to come to a stop
critical density
the value of density that would create a flat universe (about 30 protons per cubic meter)
dark matter
matter we cannot observe because it is not radiating enough for us to detect it
nucleosynthesis
the creation of nuclei of different elements as a result of fission reactions
Chandraeskhar limit
1.4 solar masses; below this limit, final stage is white dwarf, above, either neutron star of black hole
planetary nebula
hot gas surrounding a dying star that consists of material expelled by the star
neutron star
a star composed of neutrons that collapsed under its own gravity
black hole
an extremely dense region of space resulting from the collapse of a red supergiant
pulsars
cosmic sources of very weak radio wave energy that pulsate at rapid and precise frequency
Hubble constant
ratio of a how fast a galaxy is moving away from Earth to its distance from Earth


Relativity (Option H) - adamblackburn adamblackburn
proper time
the time measured in a frame of reference at rest with respect to events
inertial mass
the property of an object that determines how much it responds to a given force
gravitational mass
the property of an object that determines how much gravitational force it feels when near another object
inertial frame of reference
a frame of reference in which the laws of inertia (Newton's laws) apply
light clock
an imaginary device in which time is measured by light bouncing between two mirrors
proper length
the length of an object recorded in a frame where the object is at rest
rest mass
the mass of an object as measured in a frame where the object is at rest
Schwarzchild radius
the point where the escape velocity is equal to the speed of light (the point of no return)
event horizon
same as the Schwarzchild radius